This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The Stem Cell Program (Dalton) has demonstrated that both mouse ESC and human ESC, when differentiated into all pathways tested thus far, begin to express polysialic acid (PSA) on their surfaces, as evidenced by anti-PSA antibody binding. This finding was suggested by changes in PSA synthetic glycosyltransferase transcript upregulation. The Subproject focuses on determining the mechanisms of expression of PSA during differentiation and its function. The scope of the subproject encompasses glycogene transcription regulation, acceptor protein expression, and development of technologies to identify the mechanism of regulation. In sum, this project demonstrates the utility of the Glycotranscriptomics Core in directing subsequent experiments to identify glycan changes during ESC differentiation. Intriguingly, both mouse and human differentiation pathways show similar glycan changes. This is by contrast to SSEA-1 and SSEA-3, two differentiation stage-specific glycans found during mouse ESC differentiation which are not found in human ESC differentiation.